A power amplifier (PA) is an amplifier that amplifies signal power and is generally applied in the communications field. For example, in a base station in the communications field, a PA is generally used to amplify power of a to-be-transmitted signal. However, in the base station, transmit distortion of the PA causes distortion of a transmit signal that is obtained after the PA performs amplification. This affects communications quality.
To ensure communications quality, an analog predistorter system is currently used to correct distortion generated by the PA, to eliminate distortion of the signal that is obtained after the PA performs amplification. The analog predistorter system includes a master delay module, an analog predistorter (APD) core module, and an APD training module. An input end of the master delay module, a first input end of the APD core module, and a first input end of the APD training module are all connected to an input end of the analog predistorter system. An output end of the master delay module and an output end of the APD core module are separately connected to an input end of the PA. An output end of the PA is connected to a second input end of the APD training module. An output end of the APD training module is connected to a second input end of the APD core module.
The input end of the analog predistorter system receives a radio frequency signal from exterior, and separately transmits the radio frequency signal to the master delay module, the APD core module, and the APD training module. The master delay module delays the radio frequency signal to obtain a master delay signal, and outputs the master delay signal to the PA. The PA performs coupling on transmit signals generated by the PA to obtain some transmit signals, and sends the some transmit signals to the APD training module. The APD training module calculates a predistortion coefficient according to the radio frequency signal and the transmit signals generated by the PA, and sends the predistortion coefficient to the APD core module. The APD core module generates a predistortion signal according to the radio frequency signal and the predistortion coefficient, and transmits the predistortion signal to the PA. The PA amplifies a mixed signal obtained by mixing the predistortion signal and the master delay signal, to obtain a transmit signal.
The APD training module calculates and adjusts the predistortion coefficient according to the radio frequency signal and the transmit signals output by the PA. When the predistortion coefficient generated by the APD training module is accurate enough, the predistortion signal generated by the APD core module can precisely offset distortion generated by the PA, so that the transmit signal output by the PA is nearly the same as the radio frequency signal.
In a process of implementing the present invention, the inventor finds that the prior art has at least the following problem:
In the foregoing analog predistorter system, when the PA has a distortion characteristic that is not corresponding to the APD core module, distortion generated by the PA cannot be effectively offset.